Protective device for grinding machines



April 21, 1964 w. R. BACKER 3,129,538

PROTECTIVE DEVICE FOR GRINDING MACHINES 24 Fig.1

Filed July 31, 1961 2 Sheets-Sheet 1 INVENTOR WILL IAM Ii. BACKEE ATTO R N EY A ril 21, 1964 w. R. BACKER PROTECTIVE DEVICE FOR GRINDING MACHINES Filed July 31. 1961 2 Sheets-Sheet 2 MAXIMUM ALLOWABLE FOECE INVENTOR WILL/AM E BIICKEIQ ZZM'WMQ ATTORNEY United States Patent C 3,129,538 PROTECTIVE DEVICE FGR GRENDKNG MACHHIES William R. Backer, Holden, Mesa, assiguor to Norton Company, Worcester, lass, a corporation of Massachusetts Filed July 31, 1961, Ser. No. 123,677 14 Claims. (Cl. 51-466) This invention relates to machines provided with highspeed grinding or cutting wheels and especially to means for rendering such machines less dangerous to personnel in the event that the wheel explodes due to misuse and/ or undetected defects.

In my copending application Serial No. 127,956, filed July 3-1, 1961, there is provided energy dissipating means operable, by deformation in compression, to dissipate the kinetic energy produced by disintegration of the wheel both with respect to such components of the forces released which tend to lift the wheel slide from its bed and those which tend to break the wheel hood. The principal objects of this invention are to provide energy dissipating means deformable in tension; to provide energy dissipating means which is susceptible of more precise control of the maximum forces involved and the dissipation thereof; and to provide means which is economical to manufacture, can be readily installed on existing machines and can be easily replaced when it has served its purpose.

As herein illustrated, the foregoing is attained by means associated with the base of the slide in such a manner as to permit the slide to move freely in translation on the base, but will prevent lifting of the slide from the base except by deformation, and that such deformation will dissipate the forces operating to effect such lifting. The aforesaid means are in the form of tension bolts operable collectively or successively to dissipate the forces involved, are comprised of a metal of known strength, and are accurately dimensioned so as to operate up to a predetermined maximum load. The bolts are connected at one end to the base or to the slide for movement a predetermined amount relative to the base or slide and a guide or gib block is connected to their opposite ends so that a portion is situated in spaced parallel, interlapping relation with the base or slide.

The invention will now be described in greater detail with reference to the accompanying drawings wherein:

FIG. 1 is an elevation of the upper part of a machine showing a portion of the base, the wheel slide, a wheel and hood therefor and, in section, the means for dissipating the forces operating to lift the wheel slide 01f of the base;

FIG. 2 is an elevation as seen from the right side of FIG. 1;

FIG. 3 is a fragmentary vertical section to much larger scale on the line 3-3 of FIG. 1;

FIG. 4 is a graphic illustration of force versus deflection, showing the absorption of energy by several strain bolts as they successively take up the forces operating to lift the slide from the base;

FIG. 5 is a vertical section showing details of a modification of the means for dissipating the forces operating to lift the wheel slide off of the base; and

FIG. 6 is a vertical cross section of an alternative embodiment of the instant invention.

Referring to the drawings (FIGS. 1 and 2), there is shown a base 10 having at its top V-shaped and flat ways 12 and 14, respectively, slidably supporting a wheel slide 16 for translational movement in a horizontal plane. The wheel slide .16 has on it bearings for a Wheel 18 and a motor 20, the latter being operably connected to the wheel for driving the latter by belts 22 entrained about pulleys on the wheel spindle and the motor shaft. A

3,129,538 Patented Apr. 21, 1964 wheel housing 24 is fastened to the slide 16 by bolts 26.

As related in the copending application Serial No. 127,956, filed July 3d, 1961, grinding and cutting speeds are constantly being increased with improvements in wheel construction and accordingly precautions must be taken to prevent, in so far as is possible, injuries to personnel or the machine itself due to explosion or disintegration of the wheel, either by misuse or through a hidden defect. Dissipation of the energy released by such destruction of the wheel is accomplished in the aforesaid copending application by deformation of elements designed to cushion the forces of kinetic energy released by destruction of the wheel through distortion in compression. The means for dissipating this energy can be somewhat more precisely controlled by the use of elements deformable in tension. This is accomplished herein in one' form as shown in FIGS. 1 to 3 inclusive, by fastening an anchor block 28 to each side of the base 10, lengthwise of the slide. Each anchor block rests on a horizontal shoulder 30 provided on the base and is secured thereto by bolts 32. The anchor blocks 28 extend upwardly from the shoulders 30 parallel to the sides of the slide 16 to the level of grooves 34 provided in the sides of the slide. Each of the anchor blocks contains a plurality of vertically disposed holes 3 5, the lower ends 37 of which are countersunk to receive the heads 36 of strain bolts 38 having portions 40 of accurately machined cross-section and threaded ends 42. The threaded ends of the strain bolts 38 are screwed into guides or gibs 44, the inner edges of which project into the grooves 34 and are normally held therein in spaced relation to the walls of the grooves so that the slide is free to move in translation under normal conditions. As herein shown, the strain bolts are made of annealed stainless steel, however, this isnot intended to be limiting, and any suitable material may be employed which has the requisite strength and machineability.

The strain bolts 38 are placed in the holes 35 in the anchor block'and' the guides or ggibs 44screwed to their threaded portions by applying an end wrench to the heads36 which have, for this. purpose, sockets 39. The guides have holes 41 corresponding in spacing to the holes in the anchor blocks for receiving the bolts 32 and these are dropped through the holes and screwed intothe base byan end wrench. A cap 43 is screwed to the top of the guide to cover the bolt holes therein.

The counterbores may be all of the same depth, if desired; and may be long enough so that the slide is permitted to move a predetermined distance with reference to the base, which distance is designed to take full advantage of the dimension of the deformable portion 40 which dissipates the forces operating to'lift the slide fromthe base. This configuration is illustrated in FIG. 5 of the drawings. As thus constructed, the several strain bolts operate collectively to dissipate such energy. Preferably, however, the several counterbores are made of different depth so that the strain bolts operate successively, in other Words, so that energy will be dissipated in part by one or more bolts up to their point of failure, in part by other bolts up to their point of failure, and so on until all of the kinetic energy is dissipated. Asherein illus-' trated, the bolts are arranged so that those closest to the Wheel'take up theshock first, that is, the counterset portions of the holes are shortest at the left end of the block, as seen in FIG. 1, and increase in depth toward the right end. Absorption or dissipation of the energy in this fashion in successive steps is represented in FIG. 4 by the several curves plotted with force as the abscissa and deflection as the ordinate. The area under each curve represents the energy absorption of a strain bolt up to its point of failure. Each bolt acts up to its point of failure independently of the others and the destructive forces are accordingly dissipated in a series of steps.

In the embodiment of the instant invention illustrated in FIGS. 1 and 3, each of the guides or gibs 44 is fully constrained in spaced relation to the cooperating groove 34 under normal operating conditions, because the head 36 of one of the strain bolts '33 is bottomed in the countersunk portion 37 of the hole 35 which accommodates that bolt, :as illustrated best in FIG. 3.

While it will be evident from inspection of the showing in FIG. 3, in particular, that each guide or gib 4 may be arranged to repose on the top of an anchor block 28 in spaced relation to the cooperating groove 34 under normal operating conditions, even when all of the heads 36 of the strain bolts 38 are spaced from the bottoms of the countersunk portions 37 of the holes 35, as illustrated in FIG. 5, the head 36 of at least one strain bolt 38 should normally be bottomed in the countersunk portion 37 of the hole 35 in which it is located in the inverted embodiment of the instant invention illustrated in FIG. 6, in order to maintain the normal spaced relationship between the gib or guide 44 and the cooperating groove 34' in the base It).

The use of the strain bolts provides for accurately determining the point at which energy dissipation will take place in order to avoid destruction of the wheel hood and/or the machine itself for it is possible to machine the strain bolts to very accurate dimensions and to choose metals of known strength per unit of area. As each bolt breaks, the mechanical energy in the system is reduced by the amount of energy converted to heat during plastic deformation of the bolt. Knowing the energy absorbing ability of a single bolt, the number of bolts may be selected so the total energy dissipation potential equals the anticipated original energy of the system. The sequential breakage of the bolts assures that the peak forces will be reasonable.

No cushioning or energy dissipating means is employed within the hood for the wheel in this apparatus, however, it is obvious that the strain bolts may be so designed that they will begin to take up or dissipate the kinetic energy soon enough to avoid destruction of the wheel hood as well as lifting of the slide from the base. It is, of course, 'within the scope of the invention to employ energy dissipating means of the copending application of even date, in combination with the energy dissipating means disclosed herein, for example, by employing the energy dissipating means in the aforesaid application within the hood and the strain bolt energy dissipating means disclosed herein for the base of the slide.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents falling within the scope of the appended claims.

I claim:

1. In a machine having a base with a wheel slide supported thereon, a wheel on the slide and a hood housing the wheel; interlapping guides, one of which is on the slide, and means connecting the other guide to the base, said means supporting said other guide in spaced parallel relation to the one so that they do not interfere with free sliding movement of the slide on the base, and said means including tension elements operating, by deformation in tension due to abnormal forces operating to lift the slide from the base, to dissipate said forces after the slide is lifted sufliciently from the base to bring the spaced interlapping guides into mutual engagement.

2. In a machine having a base with a wheel slide supported thereon, a wheel on the slide and a hood housing the Wheel; interlapping guides, one of which is on the base, and means connecting the other to the slide so that the interlapping guides are disposed in spaced parallel relation such that they do not interfere with free sliding movement of the slide on the base including tension elements, operable by deformation in tension due to separation of the slide from the base, to dissipate the abnormal forces operating to effect such separation after the slide is lifted suliiciently from thebase to bring the spaced interlapping guides into mutual engagement.

3. In a machine having a base with a wheel slide thereon, a wheel on the slide and a hood housing the wheel; tension bolts, means connecting the tension bolts at one end to the base, and means connected to the other ends of the bolts having interlapping relation to a part of the slide, said tension bolts operating, by deformation, to dissipate the energy of forces operating to lift the slide from the base.

4. A machine according to claim 3, wherein the tension bolts are designed to resist deformation in tension up to a predetermined maximum load.

5. A machine according to claim 3, wherein the tension bolts are comprised of a metal of known strength and are precisely dimensioned to withstand tension forces up to a predetermined calculable maximum.

6. In a machine having a base and a wheel slide thereon, a wheel on the slide and a hood housing the wheel; a plurality of tension bolts, means securing the heads of the bolts to the base in such fashion that they are free to move a predetermined amount perpendicular to the base, and means secured to the opposite ends of the bolts having interlapping relation with the slide, said bolts being deformable by separation of the slide from the base by an amount greater than said predetermined amount to dissipate the energy of said forces.

7. A machine according to claim 6, wherein certain of the bolts are free to move greater distances than others so that they operate successively.

8. A machine according to claim 6, wherein the bolts are arranged to operate successively from those nearest to the wheel to those farthest therefrom.

9. In a machine having a base and a wheel slide thereon, a Wheel on the slide and a hood housing the wheel; a block bolted to the base, said block containing a plurality of vertically disposed holes, the lower ends of which are countersunk to receive the heads of bolts, headed tension bolts disposed in the holes with their heads situated in the countersunk portion thereof, and a guide secured to the upper ends of the bolts, said guide having portions in spaced parallel, interlapping relation to the slide.

10. In a machine having a base with a wheel slide thereon, a wheel on the slide and a hood housing the wheel; a block bolted to the base, said block containing a plurality of vertically disposed holes, the lower ends of which are counterbored to receive the heads of the bolts, said counterbores being of different depth, headed strain bolts disposed in the holes with their heads situated in the counterbores, and a gib block secured to the opposite ends of the bolts, said gib block having a portion in spaced parallel, interlapping relation to the slide. 11. In a machine tool having a high speed cutting tool and including first and second machine members disposed for relative sliding movement during normal machine tool operation, energy dissipating means including a first portion secured to the first machine member and a second portion disposed in interfitting spaced relation to said second machine member so that said second machine member is engaged by said energy dissipating means if said second machine member is separated abruptly from said first machine member by abnormal forces but not when said second machine member is moved slidably along said first machine member during normal operation of the machine tool, and connecting means deformable under a predetermined tension load interconnecting said first and said second portions of said energy dissipating means and operable by deformation in tension to dissipate abnormal forces released in the event of cutting tool breakage effective to separate said second machine member from said first machine member sufiiciently to engage said energy dissipating means.

12. In a machine tool having a high speed cutting tool and including first and second machine members disposed for relative sliding movement during normal machine tool operation, energy dissipating means including a first portion secured to the first machine member and a second portion disposed in interfitting spaced relation to said second machine member so that said second machine member is engaged by said energy dissipating means if said second machine member is separated from said first machine member but not when said second machine member is moved slidably along said first machine member, and connecting means deformable under a predetermined tension load interconnecting said first and said second portions of said energy dissipating means and operable, in the event of cutting tool failure, by deformation in tension to dissipate forces tending to separate said second machine member from said first machine member, said connecting means comprising a plurality of tension bolts each designed and constructed to resist deformation in tension up to a predetermined load level.

13. In a machine tool having a high speed cutting tool and including first and second machine members disposed for relative sliding movement during normal machine tool operation, energy dissipating means including a spaced pair of first portions secured to the first machine member and a spaced pair of second portions disposed in interfitting spaced relation to said second machine member so that said second machine member is engaged by said energy dissipating means if said second machine member is separated abruptly from said first machine member by abnormal forces released in the event of cutting tool breakage but not when said second machine member is moved slidably along said first machine member during normal operation of the machine tool, and a pair of connecting means deformable under a predetermined tension load each interconnecting one of said first portions and one of said second portions of said energy dissipating means and operable by deformation in tension to dissipate abnormal forces effective to separate said second machine member from said first machine member sufficiently to engage said energy dissipating means.

14. In a machine tool having a high speed cutting tool and including first and second machine members disposed for relative sliding movement during normal machine tool operation, energy dissipating means including a spaced pair of first portions secured to the first machine member and a spaced pair of second portions disposed in interfitting spaced relation to said second machine member so that said second machine member is engaged by said energy dissipating means if said second machine member is separated from said first machine member but not when said second machine member is moved slidably along said first machine member, and a pair of connecting means deformable under a predetermined tension load each interconnecting one of said first portions and one of said second portions of said energy dissipating means and operable by deformation in tension to dissipate forces tending to separate said second machine member from said first machine member, each said connecting means comprising the same predetermined number of tension bolts respectively mounted to be displaced predetermined different amounts before each bolt is tensioned so that they operate successively according to a predetermined sequence.

References Cited in the file of this patent UNITED STATES PATENTS 2,368,225 Lebermann Jan. 30, 1945 2,375,306 Koplin et a1. May 8, 1945 FOREIGN PATENTS 591,808 France July 18, 1925 554,443 Canada Mar. 18, 1958 

1. IN A MACHINE HAVING A BASE WITH A WHEEL SLIDE SUPPORTED THEREON, A WHEEL ON THE SLID AND A HOOD HOUSING THE WHEEL; INTERLAPPING GUIDES, ONE OF WHICH IS ON THE SLIDE, AND MEANS CONNECTING THE OTHER GUIDE TO THE BASE, SAID MEANS SUPPORTING SAID OTHER GUIDE IN SPACED PARALLEL RELATION TO THE ONE SO THAT THEY DO NOT INTERFERE WITH FREE SLIDING MOVEMENT OF THE SLIDE ON THE BASE, AND SAID MEANS INCLUDING TENSION ELEMENTS OPERATING, BY DEFORMATION IN TENSION DUE TO ABNORMAL FORCES OPERATING TO LIFT THE SLIDE FROM THE BASE, TO DISSIPATE SAID FORCES AFTER THE SLIDE IS LIFTED SUFFCIENTLY FROM THE BASE TO BRING THE SPACED INTERLAPPING GUIDES INTO MUTUAL ENGAGEMENT. 